Record error correction system



Dec. 3, 1968 R. E. ARKO 3,414, 13

RECORD ERROR CORRECTION SYSTEM Filed Aug. 23, 1965 I 13 E 23 DETECTION cmcurr I I l I I I 53 I H2 94 1 I 1 2| I I f 20 65 I 3 i zn 5o 1, I v FIBER; I I

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ATTORN United States Patent 3,414,673 RECORD ERROR CORRECTION SYSTEM Robert E. Arko, Mount Prospect, Ill., assignor to Teletype Corporation, Skokie, Ill., a corporation of Delaware Filed Aug. 23, 1965, Ser. No. 481,598 16 Claims. (Cl. 178-922) This invention relates to error detection and correction systems and more particularly to a system for controlling the operation of pull-back tape transmitters and overpunching reperforators.

In modern day telegraphic communications it is often desirable to transmit large blocks of numeric information. Since errors in numeric information are not as apparent as in alphabetic information it is desirable to employ error detection and correction systems in conjunction with numeric transmission equipment in order to assure the reliability of the information transmitted. Unfortunately the high cost of most error detection and correction systems has limited their use in commercial telegraph installations.

Accordingly, a principal object of this invention is to lower the cost of error detection and correction systems.

Another object of the invention is to simplify and facilitate the implementing of error detection systems.

Yet another object of this invention is to provide an error correction apparatus which is largely mechanical in nature and which employs a small number of simple circuits.

A further object of this invention is to provide an error detection and correction system which is fabricated by adding a small number of easily manufactured parts to standard pieces of telegraph apparatus.

A still further object of this invention is to provide a simple correction mechanism responsive to an error detection apparatus for obliterating an errored message and initiating retransmission thereof.

According to the preferred embodiment of the invention these and other objects are achieved by putting the retransmitting and erasing of an errored portion of a previously transmitted message under the control of pin wheel attached to the feed wheel shafts of a pull-back tape controlled transmitter and an overpunching reperforator. Each of the pin wheels carries a plurality of pins normally in a nonoperative or dormant position but capable of being set into an operative position. When an error in the message being transmitted is detected a pin on each of the pin wheels is set into its operative position. At the transmitter the transmission of the message is stopped and tape is pulled back until the pin which has been set into the operative position reaches a predetermined-position at which time normal tape feed and message transmission is resumed. At the reperforator the detection of an error causes an erasing or overpunching punch to commence operation. Obliteration of the previously recorded message continues until a pin on the pin wheel of the reperforator which is in the operative position engages an overpunch disabling switch at which time normal reperforating operations are resumed.

' A more complete understanding of the invention may be had by referring to the following detailed description when taken in conjunction with the drawing wherein:

FIG. 1 is a perspective schematic illustration of a transmitter-distributor employed in the present invention;

FIG. 2 is a perspective schematic illustration of a reperforator employing the present invention; and

FIG. 3 is a circuit schematic of an error detection and correction system embodying the present invention.

Referring now to the drawing, wherein like reference numerals designate like parts throughout the several views, with particular reference being had to FIG. 1, there will be seen a transmitting station 9 including a tape transmit- I 3,414,673 Patented Dec. 3, 1968 "ice ter 10 which operates in conjunction with a distributor 11 to read a punched paper tape and to serialize the message contained therein onto a message telegraph line 12. The transmitter 10 is of the pullback type in that it is capable of pulling back a portion of a punched paper tape previously read and re-transmitting a previously transmitted portion of a message in response to the receipt of a signal over an error line 13. A transmitter of this type is shown in J. L. De Boo Patent No. 3,014,092, granted Dec. 19, 1961. This patent discloses a transmitter in which the feed mechanism may be operated in either a forward or a reverse direction. It should be understood, however, that the invention is also applicable to transmitters in which an independent tape pull-back mechanism is used to cause the tape to move in a direction opposite to the normal direction of tape through the transmitter. The distributor 11 may be of any of the well known types, for example, it may be of the commutator and brush type.

Attached to the feed wheel shaft 14 of the transmitter 10 (this shaft corresponds to the feed wheel shaft 34 of the above-identified De Boo patent) is a pin wheel 20 which carries a plurality of contact actuating pins 21. Each of the pins 21 has a non-operative or dormant position (the majority of the pins in FIG. 1 are shown in this position) and an operative position (one of the pins 21' is shown in this position). A pin setting magnet 23 is provided for actuation upon receipt by the transmitter of signals over the error line 13, and, upon actuation its armature 24 is rocked about a pivot 25 against the action of a spring 26 and thereupon moves one of the pins 21 into the position illustrated by the pin 21. The pin wheel 20 is of a suitable dimension so that for each incremental movement of the feed wheel shaft 14 a different individual one of the pins 21 will come into alignment with an arm 27 of the armature 24 and will thereupon be positioned to be moved to its operative position by the magnet 23.

As is indicated by the arrow 30 the pin wheel 20 can move in a forward and in a reverse direction. When the wheel moves in a reverse direction any of the pins 21 which are in the operative position, as illustrated by the pin 21', will, upon being advanced a predetermined number of steps by the feed wheel shaft 14, engage a contact arm 31 and will cause a normally closed contact pair 32 to open. Upon being moved in the forward direction as indicated by the arrow 30, the pins 21 will move past a reset member 33 which serves to cam any of the pins 21 which are in the operative position back into the dormant position.

Referring now to FIG. 2, there is shown a message receiving and correcting station 39 including a reperforator 40 which is connected by the message line 12 and the error line 13 to the transmitter 10 and the distributor 11.

The reperforator 40 serves to receive signals from the transmitter and to record these signals by punching permutation combinations of holes into a paper tape. It should be understood that the reperforator 40 will normally be located at a point remote from the location of the transrnitter 10 and that the transmitter and the reperforator may be used to transmit messages over long distances. Although any of the 'well known types of reperforators may be employed, it is contemplated that the reperforator shown in Patent No. 2,951,902, granted to R. E. Arko et al. on Sept. 6, 1960, will be employed.

Mounted on top of the reperforator 40 is an error detection circuit 41. This circuit may be of any of the well known types but preferably is of the type shown in Patent No. 2,152,038, granted to L. M. Potts on June 20, 1950*. Error detection circuits of this general type sense the operation of some part of the punching mechanism, for example, the interposers or the punch pins, and give an error signal if an incorrect combination of these members is actuated. Alternatively, a tape reader may be employed to read the tape perforated by the reperforator and the circuit shown in the Potts patent may be employed in conjunction with such a reader. In any event when the error detection circuit 41 detects that an erroneous character has been punched by the reperforator 40 an error signal is transmitted by the circuit over the error line 13 to the transmitter 10.

Extending from the side of the reperforator 40 is a feed wheel shaft 44 (corresponding to the feed wheel shaft 492 of the above-identified Arko patent) upon which a pin wheel is mounted. This pin wheel is virtually identical to the pin wheel 20 which is attached to the feed wheel shaft 14 of the transmitter 10. The pin wheel 50 carries a plurality of pins 51 each of which has a dormant and an operative position and each of which may be moved from its dormant to its operative position by an arm 57 of an armature 54 which is rocked about a pivot 55 against the action of a spring 56 by a pin setting magnet 53. Like the pin wheel 20, the pin wheel 50 is of suitable dimensions so that for each incremental advancement of the tape advancing mechanism of the reperforator 40 the pin wheel 50 is advanced one step, that is, an amount sufiicient to bring the next individual one of the pins 51 into alignment with the arm 57. As is indicated by the arrow 60, the tape advancing mechanism of the reperforator 40 moves in only one direction. When a pin 51 has been moved to the operative position it eventually will engage a contact arm 61 similar to the contact arm 31 and will, upon such engagement, open a normally closed contact pair 62. Upon further movement a pin in the operative position will snap out of contact with the arm 61, will come into engagement with a resetting member 63 and will be cammed back into the dormant position by the member 63.

In addition to the components attached to the transmitter 10 there is associated with the pin Wheel 50 a cancelling member 64 which is moved by a solenoid 65 into engagement with the pin Wheel 50 and which serves to drive any of the pins 51 which is in the operative position, and which is positioned between the arm 57 of the armature 54 and the contact arm 61, back into the dormant position.

Associated with the reperforator 40 is an overpunching mechanism which serves, upon actuation, to erase or cancel characters previously recorded by the reperforator 40 by o'verpunching or obliterating these characters. The overpunching mechanism 70 is comprised of a punch block 71 in which are slidably mounted a plurality of punch pins equal in number to the total possible number of perforations in a tape which is being punched by the reperforator 40. These punch pins are cyclically operated simultaneously by a punch operating arm 72 which is eccentrically mounted on an overpunch drive shaft 73. The shaft 73 is driven by a pulley 74 which is in turn operated through a belt 75 by a pulley 76. Pulley 76 is attached to the punch operating mechanism of the reperforaLtor 40 and is revolved through one revolution each time a character is recorded by the reperforator. If the reperforator shown in the above-identified Arko et al. patent is used, the pulley may be attached to and driven by the cam sleeve 291.

The pulley 76, the belt 75 and the pulley 74 are operated through one cycle of operation each time a character is recorded by the reperforator 40. The overpunching or obliterating of the previously recorded tape is, however, effected only when a single-revolution clutch 80 mounted on the shaft 73 is released. The clutch 80 is released by a clutch release magnet 81, which upon energization, rocks its armature 82 about a pivot 83 against the operation of a spring 84. When the armature 82 is so moved it comes out of the path of a clutch stop member on the clutch 80 and thereby engages the clutch. This connects the punch operating arm 72 to the pulley 74 so that the overpunch 70 obliterates or erases one character for each one punched by the reperforator 40. When the magnet 81 is deenergized the spring 84 rocks the armature 82 into the path of the stop member 85 and, after the overpunching member 70 has completed any previously started cycle of operation, the clutch 80 will become disengaged and further cyclic operation of the pulley 74 will not effect obliteration of the tape.

A feed wheel 77 is mounted adjacent the overpunchin'g unit 70 and serves to advance tape through the overpunching unit. The feed wheel 77 is mounted on and driven by a shaft 78 which is in turn driven by a pulley 86. A belt 87 connects the pulley 86 to a pulley 89 which is mounted on the feed wheel shaft 44. This arrangement assures that the feed 'wheel 77 will be advanced each time the feed mechanism of the reperforator 40 is advanced and that a constant amount of tape will be maintained between the reperforator and the overpunch 70.

'The operation of the tape advancing mechanism of the transmitter 10 and of the overpunching unit 70 are controlled by the pin wheels 20 and 50 through the circuit schematically illustrated in FIG. 3. In that figure the error detection circuit 41 is shown attached to the error line 13 which extends over a distance illustrated by the dotted portion of the line 13 to the remote transmitting station 9 that is sending the message to the message receiving and correcting station 39. Whenever the error detection circuit 41 detects an error in the character recorded by the reperforator 40 it applies current to the error line 13 for a period of time approximately equal to one cycle of operation of the reperforator. The application of current to the error line 13 causes a line relay 90, which is located at the transmitting station to operate.

Operation of the line relay 90 closes a contact pair 94 and thereby connects a source of potential 91 to the pin setting magnet 23 of the transmitter 10 through a lead 92, normally open, now closed contact pair 94 and a lead to said magnet. This causes the pin setting magnet 23 to operate which in turn causes a pin 21 of the pin wheel 20 to be moved to the operative position. Operation of the line relay 90 also closes a contact pair 96 and thereby connects the positive source of potential 91 through the lead 92, a lead 98 and a normally open, now closed, contact pair 96 to a reverse tape feed control magnet 97. Upon such connection, the reverse feed control magnet 97 operates and upon operation locks up through a circuit including normally open, now closed contact pair 110, a lead 111, the normally closed contact pair 32 associated with the pin wheel 20, a lead 112 and the lead 98.

Operation of the reverse feed control magnet 97 operates transfer contact 115 which, upon actuation, opens a normally closed circuit including a forward feed magnet 116 and a read magnet 117 of the transmitter 10 and closes a normally open circuit from the power source 91 to a reverse feed magnet 118 of the transmitter 10. These magnets correspond to forward feed magnet 106, read magnet 146 and reverse feed magnet 67 of the aboveidentified De Boo Patent No. 3,014,092. This operation causes the transmitter to stop feeding tape in the normal direction, to stop reading the tape and to start feeding the tape in a reverse direction.

Once started, reverse feeding of the tape continues until one of the pins 21 which has been moved to its operative position by the actuation of the pin setting magnet 23 comes into contact with the contact arm 31. At this time the holding circuit for the reverse feed control magnet 97 is broken by the opening of the contact pair 32. This allows the magnet 97 to deenergize which in turn causes the transfer contact 115 to reclose the circuit from the power source to the forward feed and read magnets 116 and 117 of the transmitter 10. This causes normal tape feed and reading operations to resume. The deenergization of the magnet 97 also causes the circuit including the reverse feed magnet 118 to be opened thereby deenergizing that magnet.

Forward feeding of the tape causes the pin 21 which had been set in the operative position to be advanced in the forward direction as indicated by the arrow 30. The

pin is stepped around past the arm 27 of the armature 24 until it contacts the reset member 33 at which time it is cammed back to the dormant or inoperative position. If an error is detected by the error detection circuit 41 during the retransmission of the previously pulled back portion of the message, the setting of a pin in the operative position and the initiation of reverse feeding proceed in the manner previously described. The stopping of reverse feeding and the starting of forward feed and retransmission occurs, however, when the pin 21 which was moved to the operative position at the detection of the first error engages the contact arm 31 due to the fact that the originally set pin will not have been moved back to the inoperative position since it will not have advanced past the arm 57. Accordingly, if an error occurs during retransmission the tape is pulled back only to the point of original pull back. The pin which is set in the operative position upon the detection of the second error has no effect on the retransmission and is merely cammed back to the dormant position whenever it reaches the reset member 33.

A line relay 120 similar to the line relay 90 is provided at the reperforator 40 for controlling the operation of the rub-out mechanism 70. The line relay 120 may be operated in a manner identical to the operation of the relay 90 by connecting the error line 13 through the coil of the relay 120. In some situations, however, it may be desirable to operate the relay 120 by the output of a circuit 119, such as the circuit shown and described in the copending application of J. A. Johnsen, Ser. No. 302,358, filed Aug. 15, 1963, which detects the absence of transmission of characters over the message line 12 by the transmitter 10. Such an absence of transmission will occur upon the detection of an error by the circuit 41 since the operation of the reverse feed magnet 97 causes the circuit to the forward feed magnet and the read magnet of the transmitter to be open and thereby prevents transmission of characters by the transmitter 10. As a final alternative a suitable relay circuit may be primed by the operation of the error detection circuit 41 and may then be triggered by a circuit, such as the aforementioned Johnsen circuit, which detects a long absence of a transmission from the transmitter 10. The choice of one or the other of these systems depends upon the time interval necessary to be sure that the last character transmitted by the transmitter 10 has been received by the reperforator 40.

Upon energization the relay 120 closes a normally open contact pair 124 and thereby connects a source of potential 121 and a line 122 to the pin setting magnet 53 and the cancelling solenoid 65, thereby operating them. The operation of the magnet 53 and the solenoid 65 causes any previously set pin 51 which lies between the arm 57 of the armature 54 and the contact arm 61 to be moved back to its dormant position by the cancelling member 64 and a new pin 51 to be moved to its operative position by the arm 57.

Operation of the relay 120 also operates an overpunching magnet 127 by connecting the source of potential 121 through the lead 122, a normally open, now closed, contact pair 126 and a lead 128 to the magnet 127. Upon energization the overpunch control magnet 127 locks up and holds through a circuit including the power source 121, the lead 122, a normally open, now closed, contact pair 140, a lead 141, the contact pair 62, the contact arm 61 of the reperforator 40, a lead 142 and the lead 128. Operation of the magnet 127 also operates the clutch trip magnet 81 by closing a normally open contact pair 145 which, upon closing, connects the power source 121 through thet magnet 81 to ground.

Operation of the magnet 81 causes the obliteration of previously recorded characters by the overpunching unit 70 until the energizing circuit for the clutch trip magnet 81 is broken. This occurs when a pin on the wheel 50 in the operative position engages the contact arm 61 and thereupon opens the normally closed contact pair 62. This operation breaks the holding circuit for the magnet 127 thus allowing the contact pair 145 of the magnet 127 to reopen the circuit to the clutch trip magnet 81. This operation will disable the overpunching unit 71 after completion of a previously begun cycle.

After the overpunch unit has been disabled by the opening of the contact pair 62, further advancement of the tape in the reperforator causes pin wheel 50 to rotate further in the direction of the arrow 60 and thus brings the pin 51 into engagement with the reset member 63 to be cammed thereby back into its dormant position. If an error is detected during retransmission the operation of the relay 120 proceeds as previously stated. The cancelling member 64 resets the previously set pin 51 back into its dormant position. The pin setting magnet 53 moves a new pin 51 into the operative position and overpunching continues until the pin 51 which was set in the operative position by the detection of the second error engages the contact arm 61.

It should be noted that in all cases the same number of characters are overpunched by the overpunching mechanism 70 as are retransmitted by the transmitter 10, This is "because the total number of characters retransmitted by the transmitter is equal to the number of reverse feeding steps taken by the pin wheel 20 from the time a pin 21 is set by the magnet 23 until the con tact arm 31 is engaged by a pin set in the operative position plus the total number of reverse steps taken by the pin wheel 20 upon the detection of an error during retransmission. The total number of characters overpunched by the overpunching unit 70 is equal to the total number of steps necessary for the pin wheel 50 to advance a pin 51 in its operative position from the arm 57 to the contact arm 61 plus the total number of steps taken before the detection of a second error. Since the total number of steps taken before the detection of a second error is equal to the number of steps taken in the forward direction, as indicated by the arrow 30, by a pin 21 set upon the detection of a first error by the magnet 23 after opening the contact pair 32, it is thus equal to the number of characters retransmitted a second time by the transmitter 10. This construction assures that the number of characters obliterated by the overpunch 70 is equal to the number of characters retransmitted by the transmitter 10.

The operation of the present invention proceeds from the detection of the recording of an error by the error detection circuit 41. Upon such detection the circuit 41 operates to momentarily apply an error signal to the line 13 and thereby serves to operate the line relay 90. Operation of the line relay causes a pin 21 on the pin wheel 20 of the transmitter 10 to be moved into its operative position. Operation of the relay 90 also causes the transmitter 10 to stop feeding tape in the forward direction, stop transmitting characters and start feeding tape in the reverse direction. The reverse feeding of the tape by the transmitter 10 causes the pin on the pin wheel 20 which has been set in the operative position to count backwards until the proper length of tape to be retransmitted has been measured. At this time the pin 21 which is in the operative position opens the contact pair 32 and thereby causes retransmission of a previously transmitted portion of the tape to begin. If an error is detected during retransmission, the tape is pulled back only to the point of original pull back since the pin 21 which was set upon detection of the original error is not moved back to its dormant position until after it has passed the pin setting mechanism.

Detection of an error also causes operation of the line relay which is similar to relay 90. Operation of the relay 120 causes a pin 51 on the pin wheel 50 to be moved to the operative position and initiates operation of the overpunching mechanism 70. The overpunching r mechanism 70 erases one character for each character recorded by the reperforator 40 until the pin 51 which is in the operative position counts a number of characters equal to the number retransmitted by the transmitter 10. After the passage of the proper amount of tape through the reperforator 40 has been measured by the pin Wheel 50, the contact pair 62 is opened by the pin 51 in the operative position and the operation of the overpunch unit 70 is thereby discontinued. Should an error occur during retransmission the cancelling mem ber 64 moves the previously set pin 51 back to the dormant position while the pin setting mechanism moves a new pin to the operative position. This assures that the same number of characters will be erased by the overpunching unit 70 as are retransmitted by the transmitter 10.

Although only one embodiment of the invention is shown in the drawings and described in the foregoing specification, it will be understood that the invention is not limited to the specific embodiment described, but is capable of modification and rearrangement and substitution of parts and elements without departing from the spirit of the invention.

What is claimed is:

1. A telegraphic transmission system including:

a tape controlled transmitter having means for feeding tape in a normal and in a reverse direction;

a recorder for receiving messages transmitted by the transmitter and having means for erasing message portions after they are received;

means for detecting the recording of an erroneous character by the recorder;

means responsive to the detection of an erroneous character by the detecting means for causing the transmitter to stop advancing tape in the normal direction, to stop transmitting and to start retracting tape in the reverse direction;

means for measuring the amount the tape is retracted and for producing an output whenever a predetermined amount of tape is retracted in the reverse direction;

means responsive to an output from the measuring means on the transmitter for causing the transmitter to stop retracting tape in the reverse direction, to start advancing tape in the normal direction and to resume transmitting:

means responsive to the detection of an error by the detecting means for causing the recorder to erase a portion of a previously recorded message upon such detection; and

means for measuring the amount of tape which is fed through the recorder after the erasure of the message is commenced and for stopping the erasure of characters after an amount of tape equal to the amount of tape retracted by the transmitter has been passed through the recorder.

2. A telegraphic transmission system including:

a tape controlled transmitter having means for feeding tape character-by-character in a normal and in a reverse direction for transmitting messages to remote points;

a reperforator having means for advancing tape and and for recording messages received from remote transmitters on the tape and having means for erasing message portions after they are received;

an error detecting circuit for detecting the recording of an erroneous character by the reperforator;

reversing means responsive to the detection of an erroneous character by the error detecting circuit for causing the transmitter to stop feeding tape in the normal direction, to stop transmitting and to start feeding tape in the reverse direction;

counting means operatively connected to the tape feeding mechanism of the transmitter and advanced there- 'by one step each time the tape is fed one character for counting the number of characters in the tape which are fed in the reverse direction by the tape feeding mechanism of the transmitter and for producing an output whenever a predetermined number of characters have been fed in the reverse direction;

means responsive to an output from the counting means of the transmitter for disabling the reversing means and for thereby causing the transmitter to stop feeding tape in the reverse direction, to start feeding tape in the normal direction and to resume transmitting;

means responsive to the detection of an error by the error detection circuit for causing the reperforator to erase a portion of a previously recorded message; and

means for counting the number of characters erased by the reperforator and for stopping the erasure of characters after a number of characters equal to the number of characters fed by the transmitter in the reverse direction have been erased by the reperforator.

3. An error detection system for a telegraphic transmission system having a tape controlled transmitter with means for feeding tape in a normal and in a reverse direction and a reperforator for receiving messages transmitted by the transmitter and having means for erasing message portions after they are received, including:

means for detecting the recording of an erroneous character by the reperforator;

mean-s responsive to the detection of an erroneous character by the detecting means for causing the transmitter to stop transmitting and to start feeding tape in the reverse direction;

means for measuring the amount the tape is fed in the reverse direction and causing the transmitter to resume advancing tape in the normal direction and to resume transmitting whenever a predetermined amount of tape sufficient to assure the transmission of the errored character is fed in the reverse direction;

means responsive to the detection of an error by the detecting means for causing the reperforator to erase an derrored portion of a previously recorded message; an

means for counting the number of characters erased by the reperforator and for stopping the erasure of character-s after a number of characters equal to the number of characters retransmitted by the transmitter have been erased, thereby assuring that the errored character will be erased and retransmitted.

4. In a message transmission system having a tape controlled pull back transmiter and an overpunching reperforator, an error detection and correction system including:

a pair of counting wheels one operatively connected to the tape advancing mechanism of the transmitter and one operatively connected to the tape advancing mechanism of the reperforator;

a plurality of switch actuating members each normally positioned in a dormant position on one of the counting wheels and individually settable to an operative position on the counting wheel;

setting means positioned adjacent each of the counting wheels for receiving signals and, upon receipt of such signals, for moving one of the switch actuating means on the wheel adjacent to it into the operative position;

means for detecting an error in a message transmitted from the transmitter to the reperforator and upon such detection, for causing the transmitter to pull back a portion of previously read tape, for causing the reperforator to start over-punching a portion of the previously recorded message and for signaling the setting means thereby causing them to move at least one of the switch actuating means on each of the counting wheels out of the dormant position for producing an output when such a signal is reand into the operative position; ceived,

a switch mounted adjacent the mounting wheel on the means responsive to the output of the receiving means transmitter for engagement by any of the switch for causing the feed means to feed tape through the actuating means on that counting wheel which is transmitter in the reverse direction, and in the operative position and, upon engagement for means for counting the number of steps which the causing the transmitter to stop pulling back tape and feed means feeds the tape in the reverse direction to start retransmitting a previously transmitted porand for causing the feed means to feed tape in the tion of the message; and normal direction when a predetermined count is a switch positioned adjacent the counting wheel on the reached.

reperforator for engagement by any switch actuating 8. In a transmission system, apparatus for causing a means on that counting wheel which is in the operatape controlled transmitter capable of feeding tape in tive position and, upon engagement, for causing either a forward or a reverse direction to, upon the transthe reperforator to stop overpunching previously mission of an error, retransmit a portion of a previously received characters so that the retransmitted portion transmitted message including: of the message will not be overpunched. a plurality of switch actuating members each having 5. In a message transmission system having a tape an operative and a dormant position and all mounted controlled pull back transmitter and an overpunching on a wheel which is operatively connected to the reperforator, an error detection and correction system intape feeding mechanism of the transmitter and which cluding: is advanced thereby a predetermined amount for a pair of pin wheels one operatively connected to the each incremental advance of the tape;

tape advancing mechanism of the transmitter and error indicating means for receiving signals indicating one operatively connected to the tape advancing the transmission of an incorrect signal by the transmechanism of the reperforator; mitter and for moving one of the switch actuating a plurality of pins mounted on the pin wheels and normembers from its dormant to its operative position; mally positioned in a dormant position and indimeans responsive to the receipt of an error indicating vidually settable in an operative position; signal by the error indicating means for causing the a pair of pin setting electromagnets each for operation transmitter to retract the tape in a reverse direction;

and

to set a pin on one of the pin wheels; means for detecting an error in a message transmitted means for actuation by any of the switch actuating from the transmitter to the reperforator and upon members which is in its operative position and, upon such detection, for causing the transmitter to pull actuation, for causing the transmitter to advance back a portion of previously read tape, for causing tape in the forward direction so that a portion of the reperforator to start overpunching a portion of the message which was previously transmitted will the previously recorded message and for causing the be retransmitted. pin setting electromagnets to move at least one pin 9. In a transmission system, an apparatus for conon each of the pin wheels out of the dormant positrolling the operation of a pull back tape transmitter intion and into the operative position; cluding: means for engagement by any pin on the pin wheel a pin wheel constrained to rotate with the feed wheel connected to the transmitter which is in the operative of the tape reader; position and, upon engagement for causing the transpin setting means for moving a pin on the pin wheel mitter to stop pulling back tape and to start retransout of an inoperative position on the pin Wheel and mitting a previously transmitted portion of the mesinto an operative position; Sage; and means for receiving a signal indicative of an error in means for engagement by any pin on the pin wheel the message being transmitted and for operating the connected to the repertorator which is in the operapin setting means on receipt of such a signal; tive position and, upon engagement, for causing the feed controlling means responsive to the operation of reperforator to stop overpunching previously rethe receiving means for reversing the direction of ceived characters so that the retransmitted portion tape feed in the tape transmitter, and of the message will not be overpunched. means for actuation by a pin on the pin wheel in the 6. In a transmission system, apparatus for controlling operative position and, upon such actuation, for disthe operation of a tape controlled transmitter capable abling the feed controlling means thereby re-reversof feeding tape in either a forward or a reverse direction ing the direction of tape feed in the tape transmitter.

10. In a transmission system, an apparatus for conincluding:

means for measuring the movement of tape through trolling the operation of a pull back transmitter which the transmitter in the reverse direction; reads tape and which transmits messages contained there error indicating means for receiving signals indicating in i cluding:

the transmission of an incorrect signal by the tra sa pin wheel constrained t0 rotate With the fCCd wheel mitter; 0f the tape reader;

a pin setting electromagnet for moving a pin on the means responsive to the receipt of an error indicating 0 pm wheel out of an inoperative position and into an signal by the error indicating means for causing the transmitter to feed tape in a reverse direction, and Operatlve posltlon; means for causing the transmitter to feed tape in the a normally ope energlzmg ell-cult for the pm settmg forward direction after the measuring device has flecmimagnet measured a predetermined amount of reverse move a ne re ay for receiving a signal mdrcatrve of an error 1n the message being transmitted and for closlng the f of the tape feedmg mechamsm of the trans energizing circuit for the pin setting electromagnet mltteron receipt of such a signal so that the magnet is a message tFaQSImSPIOH System, apparatus for operated and a pin on the pin wheel is set into the controlling a tape transmitter including: operative position;

feed means for feeding tape in a step-by-step manner feed controlling means responsive to the operation of through the transmitter in a normal direction and the line relay for reversing the direction of tape feed in a reverse direction, in the tape transmitter and for interrupting the transmeans for receiving signals indicative of an error in mission of the message; and

a message being transmitted by the transmitter and means for actuation by a pin on the pin wheel in the operative position and upon such actuation for disabling the feed controlling means thereby re-reversing the direction of tape feed in the tape transmitter.

11. A tape transmitter control mechanism comprising:

feed means including a feed wheel mounted on a feed wheel shaft for feeding tape in a step-by-step manner through the transmitter in a normal direction and in a reverse direction;

means for receiving signals indicative of an error in a message being transmitted by the transmitter and for producing an output when such a signal is received;

means responsive to the output of the receiving means for causing the feed means to feed tape through the transmitter in the reverse direction;

a pin wheel mounted on the feed wheel shaft for rotation by the feed means in a normal and in a reverse direction corresponding to the direction of feeding of the tape;

means responsive to the output of the receiving means to set a pin on the pin wheel; and

means for engagement by a set pin on the pin wheel and for causing, upon such engagement, the feed wheel to stop feeding tape in the reverse direction and to resume feeding tape in the normal direction.

12. In a transmission system, apparatus for controlling the operation of a reperforator capable of obliterating a portion of a message previously punched including:

measuring means for measuring the amount of tape which passes through the reperforator;

error detection means for detecting the punching of an incorrect character by the reperforator;

means responsive to the detection of a failure by the error detection means for causing the reperforator to obliterate a portion of a message previously punched and for causing the measuring means to start measuring the passage of tape through the reperforator; and

means for stopping the overpunching of characters after the measuring device has measured the passage of a predetermined amount of tape through the reperforator.

13. In a message transmission system, apparatus for controlling a message recorder including:

erasing means for cyclic operation to obliterate individual characters previously recorded by the recorder;

error detection means for detecting the recording of an erroneous character by the recorder and for producing an output when such a detection is made;

transmission means responsive to the output of the detection means for operatively connecting the erasing means to the drive mechanism of the recorder so that the erasing means obliterates one character for each character recorded by the recorder; and

means operatively connected to the recorder for counting the number of characters recorded by the recorder after the detection of an error by the error detecting means and for disabling the transmission means after a predetermined count is reached thereby disconnecting the erasing means from the recorder and stopping the obliteration of characters.

14. In a transmission system, apparatus for controlling the operation of a reperforator capable of deleting a portion of a message previously punched including:

a plurality of switch actuating members each having an operative and a dormant position;

a supporting element for said switch actuating members operatively connected to the tape advancing mechanism of the reperforator and which is advanced thereby a predetermined amount for each incremental advance of the tape;

error detection means for monitoring the operation of the reperforator and for detecting the punching of an incorrect character by the reperforator;

means responsive to the detection of an error by the error detecting means to move one of the switch actuating members out of its dormant position and into its operative position;

means responsive to the detection of an error by the error detection means for causing the reperforator to delete a portion of a message previously punched; and

means for actuation by any of the switch actuating members which is in its operative position and, upon such actuation, for stopping the deletion of characters and for resuming the normal recording of the message.

15. In a transmission system, an apparatus for controlling the operation of an overpunching reperforator including:

a pin wheel constrained to rotate with the feed wheel of the reperforator and having a plurality of pins on it;

pin setting means for moving a pin on the pin wheel out of an inoperative position on the pin wheel and into an operative position;

means for detecting the receipt of an erroneous character by the reperforator and for operating the pin setting means upon such detection;

overpunching means responsive to the operation of the error detecting means for obliterating a portion of the message punched by the reperforator; and

means for actuation by a pin on the pin wheel in the operative position and, upon such actuation, for disabling the overpunching means so that no further characters are obliterated.

16. In a transmission system, an apparatus for controlling the operation of an overpunching reperforator including:

a pin wheel constrained to rotate with the feed Wheel of the reperforator and having a plurality of settable pins on it;

a pin setting electromagnet for moving a pin on the pin wheel out of an inoperative position on the pin wheel and into an operative position;

a normally open energizing circuit for the pin setting electromagnet;

means for detecting the punching of an erroneous character by the reperforator and for closing the energizing circuit for the pin setting electromagnet upon such detection;

an overpunch for cyclic operation to erase individual characters previously recorded by the reperforator whenever the detecting means detects the punching of an erroneous character by the reperforator;

means for operatively connecting the overpunch to the reperforator so that the overpunch operates through one complete cycle for each cycle of operation of the reperforator; and

means for actuation by a pin on the pin wheel in the operative position and, upon such actuation, for disabling the overpunch so that no further characters are obliterated.

References Cited UNITED STATES PATENTS 2,975,407 3/ 1961 OBrien. 3,002,681 10/ 1961 Norton et al. 3,144,205 8/ 1964 Turner. 3,208,041 9/ 1965 Swenson.

THOMAS A. ROBINSON, Primary Examiner. 

1. A TELEGRAPHIC TRANSMISSION SYSTEM INCLUDING: A TAPE CONTROLLED TRANSMITTER HAVING MEANS FOR FEEDING TAPE IN A NORMAL AND IN A REVERSE DIRECTION; A RECORDER FOR RECEIVING MESSAGES TRANSMITTED BY THE TRANSMITTER AND HAVING MEANS FOR ERASING MESSAGE PORTIONS AFTER THEY ARE RECEIVED; MEANS FOR DETECTING THE RECORDING OF AN ERRONEOUS CHARACTER BY THE RECORDER; MEANS RESPONSIVE TO THE DETECTION OF AN ERRONEOUS CHARACTER BY THE DETECTING MEANS FOR CAUSING THE TRANSMITTER TO STOP ADVANCING TAPE IN THE NORMAL DIRECTION, TO STOP TRANSMITTING AND TO START RETRACTING TAPE IN THE REVERSE DIRECTION; MEANS FOR MEASURING THE AMOUNT THE TAPE IS RETRACTED AND FOR PRODUCING AN OUTPUT WHENEVER A PREDETERMINED AMOUNT OF TAPE IS RETRACTED IN THE REVERSE DIRECTION; MEANS RESPONSIVE TO AN OUTPUT FROM THE MEASURING MEANS ON THE TRANSMITTER FOR CAUSING THE TRANSMITTER TO STOP RETRACTING TAPE IN THE REVERSE DIRECTION, TO START ADVANCING TAPE IN THE NORMAL DIRECTION AND TO RESUME TRANSMITTING; MEANS RESPONSIVE TO THE DETECTION OF AN ERROR BY THE DETECTING MEANS FOR CAUSING THE RECORDER TO ERASE A PORTION OF A PREVIOUSLY RECORDED MESSAGE UPON SUCH DETECTION; AND MEANS FOR MEASURING THE AMOUNT OF TAPE WHICH IS FED THROUGH THE RECORDER AFTER THE ERASURE OF THE MESSAGE IS COMMENCED AND FOR STOPPING THE ERASURE OF CHARACTERS AFTER AN AMOUNT OF TAPE EQUAL TO THE AMOUNT OF TAPE RETRACTED BY THE TRANSMITTED HAS BEEN PASSED THROUGH THE RECORDER. 